Martin N C, Miller D L, Underbrink K, Ming X
J Biol Chem. 1985 Feb 10;260(3):1479-83.
A transcript from the yeast mitochondrial tRNAMetf gene has been isolated from a petite deletion mutant, ND40. RNA sequence analysis demonstrates that it has a 5' unprocessed extension of 28 nucleotides, and capping experiments with guanylyltransferase reveal that the first nucleotide has a 5' di- or triphosphate. A comparison of the RNA sequence with the tRNAMetf gene sequence reported here shows that transcription initiation occurs at a sequence homologous to a nonanucleotide segment implicated as a promoter element of yeast mitochondrial DNA. The 3' end of this transcript is identical to the mature tRNAMetf and carries a CCA sequence. The transcript can be processed in vitro to yield a mature tRNAMetf and thus appears to be a bona fide tRNA precursor. This tRNA precursor accumulates in the absence of the mitochondrial tRNA synthesis locus whereas mature tRNAMetf can be made from the same gene in the presence of the locus. This data provides clear and convincing evidence that the synthesis locus codes for a 5' tRNA processing function.
已从小菌落缺失突变体ND40中分离出酵母线粒体tRNAMetf基因的转录本。RNA序列分析表明，它有一个28个核苷酸的5'未加工延伸，用鸟苷酸转移酶进行的加帽实验表明，第一个核苷酸有一个5'二磷酸或三磷酸。将该RNA序列与本文报道的tRNAMetf基因序列进行比较，结果表明转录起始于与一个九核苷酸片段同源的序列，该片段被认为是酵母线粒体DNA的启动子元件。该转录本的3'末端与成熟的tRNAMetf相同，并带有CCA序列。该转录本可在体外加工产生成熟的tRNAMetf，因此似乎是一个真正的tRNA前体。这种tRNA前体在没有线粒体tRNA合成位点的情况下积累，而成熟的tRNAMetf可以在该位点存在的情况下由同一基因产生。这些数据提供了清晰而有说服力的证据，表明合成位点编码一种5' tRNA加工功能。
